1. Field of the Invention
The present invention relates to a semiconductor device capable of providing more stabilization of a voltage for operating an internal circuit based on a source voltage supplied from outside the semiconductor device and reducing a chip area.
2. Description of the Related Art
An internal source voltage has heretofore been generated by an internal source voltage generating circuit (step-down or debooster circuit or the like) provided inside a semiconductor device, based on an external source voltage supplied by a constant voltage source from outside the semiconductor device. Further, a boosted voltage higher than the internal source voltage has been generated by a booster circuit based on the internal source voltage. These internal source voltage and boosted voltage have been used to drive an internal circuit (such as a memory cell, TTL (Transistor Transistor Logic) level input buffer circuit, a data output driver circuit) employed in the semiconductor device.
In the above-described semiconductor device, however, there may be cases in which when current is consumed by the internal circuit in the semiconductor device where the internal circuit is operated using the aforementioned internal source voltage and boosted voltage, a voltage drop is developed due to the impedance of the internal source voltage generating circuit, so that the internal source voltage and boosted voltage change. Thus, there has been provided a capacitor for voltage stabilization between a node placed between the internal source voltage generating circuit and the internal circuit and a ground voltage with a view toward stabilizing the internal source voltage and the boosted voltage. A capacitor having a MOS type structure wherein a gate oxide film used for a MOS (Metal Oxide Semiconductor) transistor is used as an insulator, has been used as such a capacitor. In the capacitor having such a MOS type structure, a gate electrode thereof is electrically connected to a node provided between an internal source voltage generating circuit and an internal circuit, and a source and drain thereof are both electrically connected to a ground voltage. On the other hand, since different driving source voltages are respectively applied to an N type well for each memory cell and an N type well for a peripheral circuit, both the N type wells have physically been separated from each other.